1. Technical Field
The present invention relates to a wiper blade for wiping the surface of a window glass of vehicles.
2. Background Art
A wiper blade mounted on vehicles such as automobiles is used for wiping off such as rain, snow, insects and splash from the preceding vehicle which are attached to a window glass in order to assure the field of view of a driver. The wiper blade is mounted on the front edge of the wiper arm connected to such as electric motors and reciprocally oscillates within a wiping area which is set on the window glass surface. The wiper arm is provided with a spring therein, and the wiper blade is pressed against the window glass surface by a pressing force transmitted from the spring through the wiper arm. Thus the wiper blade can wipe off the window glass by the reciprocal oscillating and the pressing force of the wiper arm.
In order to obtain the preferred wiping performance, the pressing force from the wiper arm should be dispersed over the longitudinal direction of the blade rubber contacting the window glass surface. Thus a wiper blade in which a blade rubber and a wiper arm are connected by multi-construction assembled levers is developed and the pressing force is dispersed through the levers. As disclosed in Japanese Patent Application Laid-Open Publication No. 6-340249, the following wiper blade has been developed: a plate type elastic member is mounted over the back face of the blade rubber, and the pressing force from the wiper arm connected to the central portion of the elastic member is dispersed over the longitudinal direction of the blade rubber through the elastic member. The thickness and the width of the elastic member change in the longitudinal direction thereby the dispersed pressure according to the window glass surface to be wiped is applied to the blade rubber.
However, it has possibility that the pressing force which is dispersed to the both end portions is less than the pressing force by the wiper arm which acts on the center because a single elastic plate material is attached to the blade rubber. Additionally, elasticity generated when contacting the window glass surface, i.e. a dispersed pressing force is set depend on changing the width and thickness of the plate material, so that the wiper blade should be set according to the curvature of the window glass surface.
Further, the curvature of window glasses for vehicles is likely to be made different between various types of vehicles because of the design, so that it was necessary to set the dedicated wiper blade for each type of vehicle. Therefore, the versatility of wiper blades is reduced and the production cost of wiper blades may have to increase.
An object of the present invention is to provide the versatility of wiper blades for window glasses having different curvature.